Leucovorin-induced Hypersensitivity Reaction in a Patient with Metastatic Colorectal Cancer Treated with Cetuximab Plus FOLFOX Chemotherapy: A Case Report.

The FOLFOX regimen (combination of leucovorin, 5-fluorouracil, and oxaliplatin) is the first-line treatment for high-risk stage 2 and 3 colorectal cancer patients. While hypersensitivity reactions (HSRs) caused by oxaliplatin are commonly reported, HSRs due to leucovorin have been infrequently reported. This report aims to investigate the clinical presentation, diagnosis, and management of leucovorin induced HSRs. A 60-year-old female developed generalized edema, dyspnea, and facial redness during cetuximab plus FOLFOX chemotherapy administered for management of metastatic colorectal cancer. Because HSRs induced by oxaliplatin are commonly reported, we initially presumed an oxaliplatin-induced HSR. However, despite undergoing oxaliplatin desensitization, HSRs persisted, and they were still observed when leucovorin was administered without oxaliplatin. The patient was diagnosed with leucovorin-induced HSR and underwent leucovorin desensitization. However, the reactions recurred within 30 minutes of the initiating the desensitization. Considering unsuccessful leucovorin desensitization, leucovorin was excluded. The patient received cetuximab and oxaliplatin chemotherapy without leucovorin to date without any adverse effects. While leucovorin-induced HSRs are infrequently reported, they should still be regarded as potential adverse effects.